Sinus Bradycardia: Definition and Key Information

Introduction

Sinus bradycardia is a type of heart rhythm disorder where the heart beats slower than normal, typically below 60 beats per minute (bpm) . It originates from the sinus node , the heart's natural pacemaker.

Causes of Sinus Bradycardia

Sinus bradycardia can be seen in various situations, including: - Physiological (normal) causes : - Well-trained athletes (due to increased vagal tone) - During deep sleep - Pathological causes : - Heart-related conditions (e.g., sick sinus syndrome, myocardial infarction, myocarditis) - Electrolyte imbalances (e.g., high potassium levels) - Endocrine disorders (e.g., hypothyroidism) - Medications (e.g., beta-blockers, calcium channel blockers, digitalis) - Autonomic nervous system dysfunction (e.g., vasovagal syncope)

Symptoms of Sinus Bradycardia

Many patients with sinus bradycardia have no symptoms, but if the heart rate becomes too slow, it can lead to: - Dizziness or lightheadedness - Fatigue - Shortness of breath - Chest discomfort - Fainting (syncope) if severe

When is Sinus Bradycardia Dangerous?

Sinus bradycardia is concerning when it causes symptoms or is associated with underlying heart disease . If the heart cannot pump enough blood to meet the body's needs, it may require medical treatment.

Diagnosis and Tests

  • Electrocardiogram (ECG) : The main test to confirm sinus bradycardia.
  • Holter monitoring : 24-hour monitoring for intermittent bradycardia episodes.
  • Blood tests : Check for thyroid, electrolytes, and medication effects.
  • Echocardiogram : Evaluates heart structure and function.

Treatment Approaches

Treatment depends on whether sinus bradycardia is symptomatic: - No symptoms : Usually no treatment needed. - Symptomatic cases : - Stopping or adjusting medications that slow the heart - Treating underlying conditions (e.g., thyroid hormone replacement for hypothyroidism) - Pacemaker implantation in severe cases when the heart rate is dangerously low.

Final Thoughts

Sinus bradycardia can be a normal finding or a sign of an underlying medical condition. It is important to assess whether it causes symptoms and to rule out potential causes. If you experience dizziness, fainting, or persistent fatigue, consult a cardiologist for evaluation.

Source recommendations

1. European Society of Cardiology (ESC) Guidelines on Cardiac Pacing and Resynchronization Therapy

  1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
  2. https://academic.oup.com/eurheartj/article/42/35/3427/6358547
  3. https://pubmed.ncbi.nlm.nih.gov/34455430/
  4. https://academic.oup.com/eurheartj/article/34/29/2281/401445
  5. https://pubmed.ncbi.nlm.nih.gov/23801827/

2. American Heart Association (AHA) Guidelines on Bradycardia and Conduction Disorders

  1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
  2. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate
  3. https://pubmed.ncbi.nlm.nih.gov/30586772/
  4. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/conduction-disorders
  5. https://www.jacc.org/guidelines/bradycardia

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